Vacuum technology has been used in a variety of applications to provide an efficient and high quality method for the deposition of coating materials onto a variety of substrates.
In the application of coatings to substrates, vacuum evaporation systems, sputtering, and ion plating have been used in the past with varying degrees of success. In the early days, vacuum systems deposited materials by simply evaporating the material and allowing it to condense on the surface of the substrate. Vacuum evaporation provides high deposition rates, but has the disadvantage of being a "line-of-sight" process. Further, since there is no particle acceleration involved in the vapor deposition, adhesion can frequently be a problem. The use of cathode bombardment in the sputtering techniques overcomes to some degree the "line-of-sight" problem, and offers a wide variety of materials and generally better adhesion than does vapor deposition.
An additional plating approach is shown in U.S. Pat. No. 3,329,601 issued to Mattox on July 4, 1967 and entitled "Apparatus for Coating a Cathodically Biased Substrate from Plasma of Ionized Coating Material" whereby ions of plating material are formed in an inert gas plasma and extracted electrostatically to arrive at the substrate at a very high potential energy level. The use of the Mattox method results in good adhesion of the deposited material; however, the Mattox process does not work well for plating insulators and resulted in argon contaminated films.
A still further ion plating method is described and shown in U.S. Pat. No. Re. 30,401 reissued to White on Sept. 9, 1980 and entitled "Gasless Ion Plating" which simultaneously biases the substrate with both DC and RF signals. The White method provides evaporant ionization and static attraction resulting in a system to plate both conductors and insulators with pure gas free films.
A need still exists for an ion plating process that will coat a wide variety of articles which are irregularly shaped with irregular depressions and which provides a smooth coating surface over such irregularities. A need further exists for an ion plating process whereby conductor materials such as, for example, gold, silver or copper, can be deposited on substrates such as, for example, ceramic substrates with such an intensity of energy that a level of adhesion is obtained that makes an adhesion layer of foreign material such as nickel or chromium unnecessary.